All Chevrolet and GMC van engines are water cooled, overhead valve powerplants, using cast iron cylinder blocks and heads.
The 230 and 250 cu in., inline six cylinder engine crankshaft has seven main bearings, with the thrust taken by No. 7. This results in a very rigid crankshaft assembly. The camshaft is low in the block and driven by gears rather than the usual chains and sprockets. Fairly long pushrods actuate the valves through ball mounted rocker arms. This engine has changed very little over the years, giving a great interchangeability of parts. A major change was introduced in 1975. This is an integral cylinder head and intake manifold casting. The integral design results in better emission control and more power and economy. The 292 six, introduced in 1975, is similar to the 250 in design but with a longer stroke. It has special valves with rotators, aluminum bearings, a larger oil capacity, larger crankpins, longer connecting rods, and a number of other heavy duty features derived from its years of use in heavier trucks.
The 4.3 Liter engines are 90° V6 type, over head valve, water cooled, with cast iron block and heads. The crankshaft is supported by four precision insert main bearings, with crankshaft thrust taken at the number 4 (rear) bearing. The camshaft is supported by four plain bearings and is chain driven. Motion from the camshaft is transmitted to the valves by hydraulic lifters, pushrods, and ball type rocker arms. The valve guides are integral in the cylinder head. The connecting rods are forged steel, with precision insert type crankpin bearings. The piston pins are a press fit in the connecting rods. The pistons are cast aluminum alloy and the piston pins are a floating fit in the piston.
The small block family of V8 engines, 283, 305, 307, 350 and 400 cu in., are all derived from the innovative design of the original 1955 265 cu in. Chevrolet V8. This engine introduced the ball mounted rocker arm design, replacing the once standard shaft mounted rocker arms. There is extensive interchangeability of components among these engines, extending to the several other small block displacement sizes available in passenger cars. The 400 cu in. version differs in block design; it does not have cooling passages between the cylinders, as on the smaller V8s.
Don't confuse the Chevrolet/GMC van 400 with the big block engine used in passenger cars, identified variously as 396, 400, or 402 cu in. The small block engine can quickly be identified by the placement of the distributor at the rear.
A new V8 diesel of 6.2L (379 cu in.) was introduced for the vans in 1983. This engine is built by Chevrolet; GM's Detroit Diesel Division aided in much of the engine's design. The 379 is even stronger, component by component, than the 350 diesel. Designed "from the block up'' as a diesel, it utilizes robust features such as four-bolt main bearing caps.